The present invention relates to a method for distinguishing a desired cell type using the expression of miRNA as an indicator.
The tissues or organs of a multicellular organism are composed of many types of cells. The human body is composed of approximately 60 trillion (6×1013) cells, and there are 411 cell types known, even if only mature cells are considered. With regard to these cells, not only a technique of analyzing the function of each cell, but also a technique of distinguishing or identifying a cell type in preparation of cells for medical application has become important.
In order to identify a cell, a means for detecting a ligand that is specifically expressed on a cell surface, using an antibody, has been generally known. However, in order to detect intracellular information using an antibody, it is necessary to immobilize a target cell and/or to allow the cell to permeate through a membrane. Thus, detection using an antibody has been problematic in that it cannot be applied to fractionation of living cells. In addition, a receptor capable of specifying a cell is not necessarily present on the cell surface. Moreover, a means for classifying one factor into two factors, positive/negative (negative or positive) (i.e., a qualitative classification means), such as ligand detection using an antibody, has been problematic in that detectable combinations are limited, and thus, it is difficult to carry out a refined classification.
As a method for more specifically classifying cells, that is, as a method for quantitatively classifying cells, for example, the profiling of cells based on multivariate measurement using a microarray, next-generation sequencing, etc. has been known. In these methods, with regard to an intracellular molecule such as a protein or RNA, many types of molecules are simultaneously subjected to a quantitative measurement, or are subjected to statistical analysis such as multivariate analysis, so that the cells can be quantitatively classified. However, since the measured cells are destroyed, this method is problematic in that it is impossible to measure cells in a live state.
As a target that can be an indicator for identifying cells, microRNA (hereinafter referred to as “miRNA”) has attracted attention. As a means for detecting miRNA in living cells, a reporter assay, which is carried out by introducing a reporter construct comprising DNA or a virus into cells, has been used. However, by such a method, it is likely that the reporter construct will be incorporated into the genome of a host cell and remain. Thus, the cells identified by this method will cause problems in medical application. Moreover, detection of miRNA according to the conventional reporter assay has been directed to searching for the target gene of the miRNA, and it has not been used to identify cells.